Lab 2

Question 1

Analogous

Answer 1

when a similar character in two or more tax is not a result of a common ancestor but instead of convergent evolution (e.g. wings of an insect and wings of a bird)

Question 2

Ancestral (or plesiomorphic) Character State

Answer 2

a character state that was seen in the early ancestors of an organism (e.g. reptiles having four legs)

Question 3

Branch

Answer 3

a line on a phylogenetic tree that connects a node to a terminal taxon

Question 4

Character

Answer 4

some observable features of an organism
it can be morphological, molecular, developmental, physiological, behavioural, or ecological (e.g. either presence or absence of legs)

Question 5

Clade

Answer 5

a lineage that arose for one ancestor (a monophyletic lineage)

Question 6

Cladogram/Phylogeny/Phylogenetic Tree

Answer 6

a tree structure that represents the evolutionary relationships within a group of organisms (three terms are interchangeably)

Question 7

Convergent Evolution

Answer 7

occurs when similar characters evolve independently in two or more texa

Question 8

Character State Reversals

Answer 8

occur when a derived character reverts to an ancestral condition

Question 9

Derived (or apomorphic) Character State

Answer 9

a character state that was not seen in the early ancestors of an organism (e.g. limblessness of snakes )
a modified character state (with reference to another, ancestral, character state)

Question 10

Homologous

Answer 10

when a character in two or more taxa can be tracked back to the character in their common ancestor, or where one character state in a taxon is derived from that in another (i.e. similarity resulting from common descent)

Question 11

Homoplasy (-ies)

Answer 11

similarities in characters of different species resulting from convergent evolution and/or character state reversals, and not resulting from common descent

Question 12

Ingroup

Answer 12

the group that is now being analyzed

Question 13

Internode

Answer 13

a line on a phylogenetic tree that connects two nodes

Question 14

Monophyletic Group (also called a Clade)

Answer 14

a phylogenetic lineage composed of two or more taxa including the common ancestral taxon and all descendants

Question 15

Node

Answer 15

a branching point on a phylogenetic tree or cladogram that represents a speciation event in which one ancestral taxon gave rise to two distinct descendant taxa
branches above the node can be rotated without changing the relationship of the taxa

Question 16

Outgroup

Answer 16

a group that is thought to be closely related to the ancestor of the ingroup, but is not part of the ingroup (snakes and lizards)

Question 17

Paraphyletic Group

Answer 17

a group composed of the common ancestral taxon and some, but not all, descendants

Question 18

Parsimony

Answer 18

the scientific preference for the simplest possible explanation that will explain some data

Question 19

Polyphyletic Group

Answer 19

a group that does not include the common ancestor

Question 20

Sister Group

Answer 20

a grouping on a phylogenetic tree where two groups are more closely related to each other than any other group

Question 21

Synapomorphy

Answer 21

a shared, homologous, derived character state (e.g. all snakes are limbless, so limblessness is a synapomorphy for snakes)